In potentially explosive areas, on drilling rigs, for example, the electrical energies present on external electronic interfaces of an electronic device may ignite a gas-air mixture which exists in this potentially explosive area and cause it to explode. This applies in particular when reactive gas mixtures are used, for example mixtures of hydrogen and oxygen, for which said electrical is available as activation energy to trigger an exothermic reaction between hydrogen and oxygen.
A similar set of difficulties exists for sound-generating loudspeakers and their electric voice coils for providing the motive force to the loudspeaker membrane. In the event of a malfunction, in particular an interruption in the electric current flow through the voice coil because of a broken electrical conducting path, a very high induction voltage can be generated by the voice coil, which may consequently result in an undesirable spark ignition. A similar phenomenon occurs if the loudspeaker overheats due to a malfunction, and this may also result in an undesirable glow ignition.
In order to prevent spark or glow ignition in a loudspeaker even if a malfunction occurs, so that they can be used in potentially explosive areas, conventional loudspeakers must not be operated with high electrical power. This in turn means that with loudspeakers of such kind only a small output power can be converted into sound waves, and consequently the sound levels achievable with such loudspeakers are limited.
Patent CN 202 602 842 U discloses a loudspeaker arrangement for use in such a potentially explosive area, comprising transformers connected in parallel, the primary coils of which can be connected electrically to an electrical power unit, while the secondary coils are each connected electrically to voice coils of two loudspeakers. In this arrangement, the first and second winding ends of the secondary coils are electrically connected to a first connector path and to an additional first connector path which forms a parallel circuit with the first connector path, and to a second connector path and an additional second connector path which forms a parallel circuit with the second connector path.